Have you had a look at AsiaRF[1]? If you are building an access point you are probably looking for more specific cards. You do miss out on things like hardware offloading if you go down that route afaik though but it may not matter due to the extra processing power you tend to get.
I don't know much about it but things like DBDC/MIMO are probably wanted. Other people may be able to comment more about this though.
I just went down the route of using a Banana Pi R3 with OpenWRT in the end though[2]. The R4 does exist now with Wifi 7 though[3].